The official date for the 1800 Census is 4 August, 1800. On this census his name was spelled 'William Pickle.'

There is one male between 16 and 25; William would have been 24. There are three females: one under 10, one between 10 and 15 and one 16-25 (this was probably Elizabeth Wilson Pickle who would have been 18).

Three lines down there appears to be a James Wilson. If so, could this have been Elizabeth's father?

[S301] 1830 Federal Census, Anderson County, South Carolina (Ancestry page 95 of 166).
Male of five and under ten: Obediah (7)
Male of ten and under fifteen: William (10), Crawford (13), and ?
Male of fifteen and under twenty: James (15)
Male of twenty and under thirty: Jacob (22)
Male of fifty and under sixty: William (54)
Female of ten and under fifteen: Jane (15), Theresa (17) (Wrong age grouping?)
Female of forty and under fifty: Elizabeth (48)

[S98] 1840 Federal Census, Anderson County, South Carolina (Ancestry page 258 of 642).
Two males fifteen and under twenty: Obadiah (17) and William (19)
One male sixty and under seventy: William (64)
Two females twenty and under thirty: Jane (25) and Theresa (27)
One female fifty and under sixty: Elizabeth